This invention relates to continuous presses in general and more particularly to a control system for a continuously operating press.
Control systems for continuously operating presses with two endless revolving forming belts which extend in a pressing section opposite each other, between which a starting material is compressed in a pressing section, and each of which is equipped with a separate drive, one of the drives being provided with a speed control to keep the belt velocity constant, are known. For example, the disclosure of German Auslegeschrift No. 22 31 802 relates to the control of a press of this type. However, in the disclosed design, so-called press belts, which exert the pressure on the forming belts, are provided in addition to the forming belts.
In machines of the type in question, it is essential that, in the cake of chips wetted with a setting resin glue, which is transported on the forming belts, no upsets or tearing occur, since this would loosen the incipient bonds in the mass of chips again and result in a sheet of lower quality. However, a continuous press of the type under discussion performs a different amount of work, depending on variations in the weight per unit area. This fluctuating amount of work must be supplied via the press belts which accordingly must take up different forces. This results in varying elastic deformations and slippage, which manifest themselves as upsets and tearing in cakes. It is an object of the German Auslegeschrift No. 22 31 802 to further develop a facility of the type described in such a manner that the cake will no longer suffer damage by tearing, crack formation or upsets when being carried through the continuously operating press by the transport belt. The idea of the solution disclosed in German Auslegeschrift No. 22 31 802 is to separate the torque demand of the continuously operating press from the torque demand of the forming belt conducted through the press. Only the transport power which is present with the press open is to be transmitted via the forming belt.
With the present invention, on the other hand, the entire driving power is transmitted to the forming belts, which are driven by suitable drives coupled to deflection rolls. If the drives operate differently, one drive can easily take up the predominant power and, so to speak, drags the other drive along. The power required therefor is transmitted through the setting cake which is contained between the forming belts and is thereby subjected to shear stresses which can be the cause of excessive loosening or the cause of failure to form the bonds in the mass.